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Feasibility study for the value of pelvic ﬂ oor distension in predicting mode of birth for women undergoing Vaginal Birth After Caesarean

Philip Toozs-Hobson

^a,

*, Elizabeth Edwards

^a

, Aneta Obloza

^b

, J. Benjamin Toozs-Hobson

^d

, Helen Egan

^c

aBirminghamWomen's&Children’sNHSFoundationTrust,UnitedKingdom

bLiverpoolWomensNHSFoundationTrust,UnitedKingdom

cBirminghamCityUniversity,UnitedKingdom

dKingsCollegeLondon,UnitedKingdom

ARTICLE INFO

Articlehistory:

Received9November2020

Receivedinrevisedform4February2021 Accepted8March2021

Availableonline14March2021

Keywords:

VBAC

Predictingdelivery Ultrasound Pelvicﬂoor

ABSTRACT

Indroduction&hypothesis:WomenhavingVaginalBirth(VB)havedifferentsofttissuedynamicsto womenrequiringemergencyLowerSectionCaesareanSection(LSCS).

Aims:ToassesstheroleofultrasoundintheassessmentofLHdistensibilityinpredictingoutcomesfor womenwishingforVaginalBirthAfterCaesareansection(VBAC).Toinformsubsequenttrialdesign includingunderstandingwomensattitudestotheuseofultrasoundinpredictionofvaginalbirth Methods:Nulliparous,previousVBandpreviousLSCSunderwentatransvaginalultrasound.Thisscan lookedatthedistensibilityoftheLHandthencorrelatedwithmodeofbirth.Analysisusedlogistic regressionandROCcurvesanalysisforstaticmeasurementsanddistensibility.Asecondcohortwasalso askedabouttheirviewsastotheusefulnessofsuchatooltohelpinformontheutilityofsuchamodel.

Results:TheoriginalhypothesisconfirmedmaternalBMI,AnteriorPosterior(AP)diameteratrestandAP distensibility allbeingsignificantpredictorsofVBinnulliparouswomen.Asexpectedthisrelationshipwasalso seeninwomenwhohadpreviouslyhadavaginalbirth.OftheVBACgroup,23womenhadLSCS.Fivewere Robsoncategory,18hademergencyLSCSinlabour.25womenhadVB.Whilstthereweretrendstowardslesser distensibilityinVBACwomenwhodeliveredvaginally,noneofthesereachedsgnificance.Theconceptofthe useofscanningtoinformwomenastolikelihoodofsuccessfulvaginalbirthwassupportedbythesurvey.

Conclusion: Previouslynotedcharacteristics in nulliparouswomenfor pelvicﬂoordistension were conﬁrmed.ThisrelationshipwasnotdemonstratedfortheVBACcohort.Wewereunabletoestablish criteriaforasimpleultrasoundmodeltopredictVBinwomenwishingforVBAC.Overall,womenwould welcomesuchmodelifitwereavailable.

creativecommons.org/licenses/by-nc-nd/4.0/).

Introduction

Thethreekeycomponentsoflabourare’Power’,‘Passage’and

‘Passenger’. Historically, pelvimetry assessed the ‘Passage’ as a predictorfordelivery[1].Toozs-HobsoninhisMDthesisdemon- strateddifferencesinthephysicalcharacteristicsofthepelvicﬂoor muscles between nulliparous women who delivered vaginally comparedtothosebyemergencycaesareansection,leadingtothe hypothesisthatsofttissuecharacteristicsareanimportantcompo- nent in ability to deliver [2,3]. We wanted to look at women undergoingVBACwhorepresentahigherriskgroupforalabourand where particularly induction of labour where scar rupture and

hypoxicbirthinjuryaresmallbutsigniﬁcantrisks[4]andtheability topredictVaginalBirth(VB)maybeextremelyuseful.

Ouraimwastoconﬁrmthepreviousobservationsofnullipa- rous women and test whether this could be extrapolated to primiparouswomenwhohadhadapreviousLSCSasapredictorof modeofbirth.Thestudywasdesignedtoinformonrecruitment andpatientviewsintheirdecisionmakingandassuchwomens viewsweresoughtastowhetherdevelopingapredictionmodel wouldhaveanyutilitywithpatients.

Methods

Women were recruited prospectively. Recruitment was in 2 cohorts,theﬁrstduring2014–2015andthesecondtoinorderto completethesamplerecruitedoverafurther2-yearperiod(2017–19).

Inclusioncriteriawerewomenwithasingletonpregnancy,as there is no data examining pelvic ﬂoor biomechanics in twin

*Correspondingauthor.

E-mailaddress:p.toozs-hobson@nhs.net(P.Toozs-Hobson).

http://dx.doi.org/10.1016/j.eurox.2021.100126

ContentslistsavailableatScienceDirect

European Journal of Obstetrics & Gynecology and Reproductive Biology: X

j o u r n a l h o m e p ag e : w w w . e l s e vi e r . c o m / l o c a t e/ e u r o x

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pregnancies. We excluded women with any pre-existing con- ditionswhichmightinﬂuencedeliverymode.Recruitmentwasat anystageofpregnancy.

Participantswerecategorisedintothreegroups:

1 WomenwithonepreviouscaesareanandplanningaVBAC.

2 Womenwhoareintheirﬁrstongoingpregnancy(control1).

3 WomenhavinghadonepreviousVB(control2).

Sincethetrialgrouphasneverpreviouslybeentestedbefore therearenodatatoinformonthenumbersrequiredtotestthis hypothesis.

Recruitsunderwentatransvaginalscaninthethirdtrimester usingtheBKMedicalFlexFocus 1202ultrasoundscan machine withafrequencybetween6 16MHz,.Allscansusedarectalprobe usingboththreeandtwo-dimensionalmodes

ThescanswereundertakenbyAOandEEbothwithtrainingand supervisionfromPTH.MeasurementsweremadeoftheLHinthe longitudinalplaneand3widths(anterior,midandposterior)as wellasLHarea,measurementsweretakenatrestandatvalsalva.

Three images were captured for each assessment to allow for

artifact and ensure adequate image quality. The images were anonymised.ImageswerereviewedbyPTHand thebestimage usedformeasurement.Analysiswasblindtothemodeofdelivery.

Review of scans was performed in blocks commonly prior to delivery,removinganybias.

The distensibility was calculated as valsalva measurement minus the rest measurement/rest measurement x 100 [3,4].

Statisticalanalysis(GraphPadSoftware,Inc.)includeddescriptive statistics,ANOVAcomparisonbetweengroups,andsimplelogistic regression[5].ROCcurveswerecalculatedinthedifferentgroups.

Logistic regression was performed to determine what may be helpfulinanysubsequentmodel.

Women’s views as to the utility of such a service were sought to help inform any further grant application. The questionnaire was non validated and merely used to record views and opinions about VBAC using a more qualitative approach.Thequestionsusedananalogscale1–10torankhow strongtheirfeelingswere,andtherewasspacetoexplaintheir choice.(diagram1)

Ethicswasobtained:PLUSSMODEL(ref14/LO/1718)andPLUSS OASIS(ref:18/EM/0151).

Table1

DeliveryOutcomeofwomen.

Group Number Missingdata ElectiveLSCS(cat3–4) EmergencyLSCS(cat1–2) SpontaneousVB AssistedVB

Nulliparous(Controlgroup1) 99 1(1%) 2(2%) 22(22%) 40(40%) 34(34%)

previousspontaneousVB(Controlgroup2) 58 0 1(2%) 4(7%) 46(79%) 7(12%)

VBAC 49 1(2%) 5(10%) 18(37%) 15(31%) 10(20%)

Table2

Baselinecharacteristicsofrecruits.

StudyModeofdelivery P0VD P0LSCS P1VD P1LSCS VBACVD VBACLSCS

Age(mean,range) 30(19–44) 31(21–41) 32(19–42) 34(31–37) 31(19–40) 32(23–43)

BMI(mean,range) 27(19–48) 31(21–47) 26(18–43) 27(23–36) 28(18–48) 29(19–37)

ethnicity 59– 15– 44 3 17 10

Caucasianother 15– 6 9 2- 8 8

MeanLHareaatrest(cm2) 13.22 13.85 14.09 12.64 13.55 13.77

MeanLHareaatValsalva(cm2) 14.26 14.5 15.33 13.28 14.65 14.71

MeandistensibilityofLHarea(%) 9.41 9.86 11.01 5.89 7.94 7.79

MeanLHAPatrest(cm2) 51.66 54.82 51.72 52.18 13.55 13.77

MeanLHAPatValsalva(cm2) 52.36 54.31 54.24 49.74 14.65 14.71

MeandistensibilityofLHAP(%) 1.54 1.6 5.12 4.28 4.77 8.33

MeanLHareaatrest(cm2) 32.96 33.64 35.12 33.9 34.23 34.29

MeanLHareaatValsalva(cm2) 35.23 34.1 36.06 34.56 35.14 32.73

MeandistensibilityofLHarea(%) 7.38 1.6 3.08 1.89 1.02 3.27

Fetalweight[kg](mean,range) 3.4(1.6–6.7) 3.6(2.8–4.6) 3.3(2.1–4.3) 3.3(2.4–3.9) 3.2(2.1–4.1) 3.6(2.4–4.6) Fetalheadcircumference[cm](mean,range) 34(29–38) 35(31–39) 34(31–37) 34(30–37) 34(31–37) 35(32–38)

Table3

OthercharacteristicsforpredictingVBAC.

Variables OR(95%CI) p-value ROC–AUC p-value St.error

Maternalage 0.9(0.86–1.07) 0.5 0.5 0.6 0.08

MaternalBMI 0.9(0.87–1.08) 0.6 0.5 0.4 0.09

Ethnicity 0.58(0.16–2.06) 0.4 0.5 0.4 0.08

LHdistensibility 0.9(0.95–1.04) 0.4 0.5 0.8 0.08

APdistensibility 1(0.9–1.04) 0.8 0.5 0.4 0.09

Trdistensibility 0.9(0.89–1.03) 0.2 0.6 0.2 0.09

LHrest 0.9(0.7–1.2) 0.8 0.5 0.8 0.09

APrest 0.9(0.8–1.08) 0.7 0.5 0.9 0.09

Trrest 1(0.8–1.2) 0.9 0.6 0.2 0.09

LHValsalva 0.9(0.8–1.17) 0.7 0.5 0.6 0.09

APValsalva 0.9(0.8–1.06) 0.5 0.5 0.4 0.09

TrValsalva 1.02(0.8–1.19) 0.7 0.5 0.3 0.08

Fetalweight 0.2(0.07-0.8) 0.04 0.67 0.05 0.08

Fetalheadcircumference. 0.85(0.58–1.23) 0.4 0.5 0.5 0.09

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Results

Two hundred and six women were recruited to the study (Table1)2wereexcludedformissingdata(1innulliparousgroup and1inVBAC).DatarelatingtoindicationsforﬁrstLSCSinVBAC groupwerenotcollected.Table2showsthedemographicsofthe womeninthestudyandTable2showsdetailsofthedeliveries.

Controlgroups

The orignal ﬁndings from Toozs-Hobson in his thesis [2]

demonstrating a difference in the characteristics of how the pelvicfloorfunctionsinnulliparouswhogavebirthvaginallyand those who required emergency LSCS were confirmed a new observation confirming this in primiparous women found (Table3).MaternalBMI19wasassociatedwith90%probability ofvaginaldeliveryAUC0.68p=0.01intheprimiparouscohort (control group 2). With,again, the observation thattherewas greaterdistensibilityinthegroupdeliveringvaginallycompared withanyofthewomenfromanygroupwhodeliveredbyLSCS (Fig.1).

There was lesser distensibility in all groups delivered by emergency LSCS when compared to control group 1 (P0-VD).

ANOVA0.2

TherewaslessdistensibilityinLSCSforControlgroup1(P0)and Controlgroup2(P1)butnottheVBACgroup.ANOVAp=0.02 VBACgroupanalysis

DespitetheoverwhelmingdesireofwomentoachieveaVB,50

%weredeliveredbyLSCS.Five(10%)ofthesehadelective(cat3–4) LSCSand18(37%)emergency(cat1–2(Table2).

Unfortunately, theassociation seen in thecontrol groups to predict mode of delivery was lost in women who had had a previousLSCS.(Figs.2and3)

SimilarROCcurvesweregeneratedforlinearmeasurementsof APdiameterandthetransversemeasurements.Logisticregression forall staticand dynamic levatoranidimensionsas wellother variables i.e. BMI, age,fetal weightand headcircumference in relation to mode of delivery outcome was also undertaken (Table 4) which demonstrate that theoriginal hypothesis does notholdtrueforwomenwhohavehadaprevioustermpregnancy resultinginaCaesareansection.

FactorsassociatedwithasuccessfulVBACwerematernalBMI, distensibilityinAPdiameterandatrest,andfetalweight.Logistic Fig.1.Levatorhiatusareadistensibilityinnulliparouswomen.

Fig.2. Differencesbetweenthreegroups(P0,P1,VBAC)bysubsequentdeliverymethod.

Fig.3.ROCforlevatorhiatusdistensibilityaspredictorformodeofdeliveryVBAC AUC0.5.

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regressionshowedthatfetalweight2.1–2.4kgwasassociatedwith likelihoodofasuccessfulVBAC82–87%.ROCAUC0.67p=0.05.

(Fig.10).

Questionnaireresults

58 women completed the questionnaire. 23 (40 %) had an absolutedesiretogivebirthvaginally(score1),withafurther9 (16%)havingapreferenceforavaginalbirth(score2-3);18(31%) were neutral in their opinion (scores 4–7), 4 (7 %) had a preferencetowardsLSCS(score7–8)with4(7%)anabsolutewish tobedeliveredbyLSCS(score10).Overall56%activelywanteda VBand14%activelywantedaLSCS.

Foursalientpointswereidentiﬁedconsideringpreferredmode ofbirthwithinthefreetextof‘Afocusonbirthchoices’,‘Informed decision making’,‘Safety considerations’ and ‘Locus of control’. Theseareimportanttoidentifyaspscho-socialaspectsofbirthand donotalwaysalignwithmedicalimperativesbutimpactonbirth outcomes[6].

WomenpredominantlydesiredVB.Evenwhentheyindicated thattheywouldchooseacaesarianforotherreasons,vaginalbirth remainedthedesiredandoptimaloption‘I’mreallylookingforward toavaginaldeliveryasopposedtoacsection’.,whichwasechoed whenconsideringrecoveryafterbirth.

The test’s potential value as means of informing decisions aroundbirthoptionsalignedtothedominantpreferenceforVB.

Several women expressedthat itcouldhelp toreduce oravoid disappointment by managing expectations ‘it would create less stressduringthebirthitselfifyouknewthelikelihoodofavaginal birth’.

Safetyconsiderationswerethepredominantinfluenceronbirth choices withsomewomenwhowantedaVBchoosinga LSCS‘I wantavaginalbirthbutIfearthecomplications,soforsafetyI’mmore towards caesarean’. There was also a differentiation between electiveLSCSandemergencyLSCS,withseveralwomenhighlight- ing thatavoidinganemergencyLSCSwas moreimportantthan havingaVB,‘IwantavaginalbirthbutIfearthecomplications,sofor safety I’mmoretowardscaesarean’.Birthsafetywastheprimary consideration for having the pelvic floor scan, with only one womanvoicingreservationsabouthavingthetest‘Notsureabout theefficiency/sideeffectsofthescan’.

The majority of women indicated that the scan would help inform andgivethemadditional agencyintheirdecisions.One woman was clear that this was not something that shewould welcome, preferring a rather external locus of control ‘(I’ll do)...Whateverthedoctorsays’.Whilstthismaynotbetheview ofmostwomenitisthecasethatpregnancyandbirthareoften fearfultimesforwomen‘IwantavaginalbirthbutI’mscaredIwon’t be able to’ and that handing that control over to health professionalsisavalidwayofcoping.

Whenaskedaboutinﬂuenceondecisionmakingandchoice,3 (5%)saidnone(allofwhichhadastrongpreferenceforVB),13(22

%)wereunsureastowhetheritwouldhelpand42(72%)saidit would be useful. When asked as to whether the scan would inﬂuencetheirdecision,3(5%)womensaidnoandagainall3were setonaVB.Oftheremaining53,30(52%)wereundecided(score

4–7)and22(38%)wouldpotentiallybehighlyinﬂuenced(scoring 8–10),with12(21%)scoringitthemaximum10forinﬂuence.

When asked about inﬂuence of individualized results and decisionforbirth,5respondednone,5wereundecidedwiththe majorityof47respondeditwould.

OfthewomenplanningtoattemptVBtherewasconsiderable interestintheplaceofsuchatool,ifavailable.Assuchthetool wouldbeusefulindecisionmakingifvalidandavailable.

Themesfromthequestionnaire

Overallthequestionnaireconﬁrmedastrongdesiretogivebirth vaginallyandthescanwasseenbythemajorityasapotentially goodthing,principallyatreducingrisksandstress“Itwouldcreate lessstressduringthebirthitselfifyouknewthelikelihoodofvaginal birth”..As such, in this sample theobjective of tryingtomake childbirtheasierandreduceriskwasunderstoodandsupported withcommentssuchas“(itwouldbe)Helpfulandempoweringin decision making” and “Iwould like to beas informedaspossible before,makingmychoice-andwhatwillbesafestforbabyandme”. DespitethedesiretohaveaVBitwasinterestingthattherewas alsoanimportanceattachedbymanywomentowardsLSCSand safetyforthebirth.

Discussionandconclusion

Our resultsshowthat a testtopredictingVB,wouldinform choice.Our dataconﬁrmtheoriginal hypothesisin ourcontrol groupsofdifferentsofttissuedynamicsinnulliparouswomenand a new observation in women parous women with a previous vaginalbirth.

Unfortunately,thesecharacteristicsappeartobelostinwomen whohavehadaLSCS.

Thereareanumberofreasonswhythismaybethecase:Firstly, andprobablymostimportantly,theindicationforpreviousLSCS wasvaried,meaningthattheVBACgroupwerehighlyheteroge- neous.SomeofthesewomenwouldhavehadelectiveLCSCand thereforetheirpelviseswere“untested”inobstetrics,inothersit wasdifficultiesintheoriginallabour.Distensibilityisavariable muscular pelvic floor activitydependent onindividual circum- stances,whichmayalsohavechangedasaresultoftheoriginal trialoflabour,leadingpotentiallytoelementsofdenervationwith subsequentmusclefibreloss.Agemayalsobeafactoraswomen havingasecondbabyareonbalancelikelytobeolder.

TheseobservationshavebeenbornoutinarecentMRIbased studyonpelvicmuscleschangesinpregnancy.Onlysomeparous womenwereabletoregaintheirpelvicﬂoormusclesshapesimilar totheirnulliparouscounterpartsafterdelivery,whichsupportsthe hypothesisof pregnancy relatedsoft tissue remodelingand /or intrapartuminjury[7].

FurtherworkprobablyrequiressegregationoftheVBACwomen into more specificgroups from their initialLSCS, suchas fetal distress,failuretoprogressandelectiveLSCStoinvestigateutility ofthismeasurementfurther.Attemptingatthisworkmayrequire a significantly more sophisticated model to be developed and wouldrequireasignificantlylargerstudy.

Table4

WomensviewsofimportanceofvaginalbirthorCaesareansection.

Question unimportant undecided signiﬁcant Maximum10/10

Howimportantisaimingforanormalbirthtoyou? 3(5%) 15(26%) 16(28%) 24(34%)

howimportantwasittoavoidaLSCS 4(7%) 19(29%) 20(34%) 17(29%)

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Authorstatement

P Toozs-Hobson:concept,design, datacollection,interpretation,manuscriptpreparation

E Edwards: performing scans, data collection, manuscript preparation

A Obloza: performing scans, data collection, interpretation, manuscriptpreparation

HEgan:interpretationandmanuscriptpreparation JBenjaminToozs-HobsonManuscriptpreparation DeclarationofCompetingInterest

FinancialdisclaimerPTHhasactedasaconsultanttoContura andBostonScientiﬁc

Funding

FundingtosupportElizabethEdwardstimewas fundedbya springboardfellowshipfromBirminghamWomensandchildrens NHSfoundationtrust.

References

[1]https://pubmed.ncbi.nlm.nih.gov/28358979/.

[2]P.Toozs-Hobson,MDThesisUniversityofLondon2003.

[3]TheeffectofmodeofdeliveryonpelvicﬂoorfunctionalanatomyPhilipToozs- Hobson,JamesBalmforth,LindaCardozo,VikKhullarandStavrosAthanasiou.

IntUrogynecolJ2008;vol19:407–16.https://www.researchgate.net/

publication/5948720_The_effect_of_mode_of_delivery_on_pelvic_ﬂoor_

functional_anatomy.

[4]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2922912/.

[5]GraphPadPrismversion8.0.0forWindows,GraphPadSoftware,SanDiego, CaliforniaUSA,www.graphpad.com.

[6]Carrie,FlannaganRN.RepeatCSorVBAC?Asystematicreviewofthefactors inﬂuencingpregnantwomen’sdecision-makingprocesses.EvidenceBased Midwifery2012;10(3):80.

[7]https://doi.org/10.1016/j.cmpb.2020.105516.